ok so my vehicle starter life as a 1997 v6 42re 4x4 truck. I got it about 13 months ago 12 months ago I put in a mostly stock 5.2l with a 44re built 46re. it always ran 188-194 but when stopped with the ac on it would climb slowly up to 210 never let it get over that. about 3 months ago I was getting on the freeway and it was running 210-215 at 75mph. I had to slow down to 45 to cool it off. if I would stop it climbed up quickly. we tried all that usual stuff thermostat, fuel sync, fan clutch, radiator, nothing so we finally pulled the engine and it was a mass, lots of bearing play cylinder walls were all torn up oil was slugged in the valley. so we scrapped it and dropped in a new rebuilt crate motor did fuel sync. new radiator, fan and clutch, water pump, alternator, p/s pump. gear box.
new injectors, new throttle body with all new sensors.. 3inch exhaust no cat into a single in dual out flowmaster 40. external trans cooler. condenser. new a/c system


so if I leave the ac off and be very nice to it I can keep it at 189-194 if I stop for a long time it will warm up.

if I turn the ac on it will want to run at 199-204 if I am nice.

if I try to tow pull a hill or get over 70mph it wants to hit 210+ have to coast to cool it off.


anyone have any ideas? me 9 other techs and 3 dealers are at a loss here...

 

Plugged heater core?? These trucks are notorious for it. What happens when you turn the heat on under load. My truck never runs above 180-190 no matter what I'm doing with it....

 

I bypassed the heater core.

 

Sounds like you did all the correct things

You installed a new fan and clutch correct it may be a crappy new part my understanding is many of these after market parts suck.

If the fan and clutch checkout ok then.

My two suggestions are either install a better rad or get an electric fan to help with air flow.

 

I will double check the fan clutch I blew out my heater core and hook the heater core back up properly no difference. I thought about putting an electric fan but I can't find any place for one the plastic grill sits too close to the front of the condenser there's no room between the condenser and the radiator and the fans right up against the radiator in the back.

 

Some of these ad in electric fans mount directly to the front of the A/C condenser with pull ties and are very thin.

A thicker more turns rad may be the answer

 

Take the new stat out cold and see if it's closed. Throw it in a pan of boiling water and see if it opens fully. Does the fan match the old one for number of blades and direction of airflow? I've seen wrong direction fans put on before....